Charging an electric car at home is usually much cheaper than filling a petrol tank, but the actual figure depends on the size of your battery, how much of it you refill, what your utility charges per kilowatt-hour, and how much energy is lost on the way from the wall socket to the cells. This calculator puts those factors together to give the cost of one charge, the energy you are billed for, the miles it adds and the cost per mile.
How to use the EV charging cost calculator
- Enter the usable battery size in kWh. Manufacturers often list a gross and a net (usable) number; use the usable one.
- Set the start and end charge levels. A typical daily top-up is 20% to 80%; a full charge is 0% to 100%.
- Keep or adjust the charging efficiency. 90% is a reasonable default for Level 2 home charging.
- Enter your electricity price per kWh from your bill, or the rate shown by a public charger.
- Enter the car’s consumption in kWh per 100 miles to see the range added and the cost per mile.
To see how this compares with a petrol car, continue with the EV vs gas calculator; to see how long the charge takes, use the EV charging time calculator.
EV charging cost formula
Energy from the wall = energy stored ÷ charging efficiency
Cost = energy from the wall × price per kWh
Range added = energy stored ÷ (kWh per 100 mi) × 100
The division by efficiency is the step people miss. If the battery receives 45 kWh at 90% efficiency, the meter records 45 ÷ 0.90 = 50 kWh. The EPA’s fueleconomy.gov notes that its energy-use figures for plug-in vehicles are measured from the wall outlet, so label numbers already include charging losses; if you take consumption from the EPA label, treat it as a wall figure and set the efficiency here to 100%.
Worked example: a 75 kWh car, 20% to 80%
A car with a 75 kWh usable battery charges at home from 20% to 80%. Power costs $0.17 per kWh, charging efficiency is 90%, and the car uses 30 kWh per 100 miles.
- Energy stored: 75 × (80 − 20) ÷ 100 = 45 kWh.
- Energy from the wall: 45 ÷ 0.90 = 50 kWh.
- Cost: 50 × $0.17 = $8.50.
- Range added: 45 ÷ 30 × 100 = 150 miles.
- Cost per mile: $8.50 ÷ 150 = $0.057.
What the same charge costs at different prices
Electricity prices vary widely between home tariffs, off-peak rates and public fast chargers. The table applies the example above to a range of prices; every value is computed from the formulas.
| Electricity price per kWh | Cost of this 20→80% charge (50.0 kWh) | Cost per mile at 30 kWh/100 mi |
|---|---|---|
| $0.12 | $6.00 | $0.036 |
| $0.17 | $8.50 | $0.051 |
| $0.25 | $12.50 | $0.075 |
| $0.40 | $20.00 | $0.120 |
| $0.55 | $27.50 | $0.165 |
Where the charging cost really comes from
Home charging is billed at your residential rate, and it is the cheapest option for most owners, especially on a time-of-use plan where overnight power costs less. Workplace charging is sometimes free or subsidized. Public Level 2 chargers are priced per kWh or per hour; DC fast chargers charge the highest rates because of their equipment and demand costs. If a charger bills by the minute rather than the kWh, divide the session’s total cost by the kWh delivered to get a comparable price.
Charging losses depend on temperature, charge rate and the equipment. Cold batteries accept energy less efficiently, and a car that preconditions its battery uses additional energy. Level 1 charging at 120 V is often a little less efficient than 240 V charging because the car’s electronics draw a roughly fixed standby power for hours. If you measure your own bills with a plug-in meter, you can replace the 90% default with a figure that matches your car and your wall box.
Sources
The 33.7 kWh-per-gallon-equivalent convention, the note that plug-in labels are measured from the wall and that charging loses a small amount of energy are explained by the US EPA/DOE at fueleconomy.gov. Consumption per 100 miles for any model is listed there too.
Frequently asked questions
How much does it cost to charge an electric car?
Multiply the energy drawn from the wall by your electricity price. A 75 kWh car charged from 20% to 80% takes about 50 kWh from the wall at 90% efficiency, which is $8.50 at $0.17 per kWh.
Why do I pay for more kWh than the battery receives?
Charging converts AC from the grid to DC for the battery, and some energy turns to heat in the charger, cables and battery. Losses of roughly 10–15% are typical at home; the calculator divides the energy stored by the efficiency to find what you are billed for.
Is public fast charging more expensive than home charging?
Usually yes. Public DC fast charging is commonly priced well above residential electricity rates. Enter the per-kWh price from the charger’s app to see the cost of a session.
How many kWh does an EV use per 100 miles?
Most passenger EVs use roughly 25–35 kWh per 100 miles at the battery. The EPA lists the figure for every model at fueleconomy.gov; enter it in the consumption box to get the cost per mile.
What if my electricity has time-of-use pricing?
Run the calculator with the off-peak price for overnight home charging. The difference between peak and off-peak rates is often large enough to cut your charging bill by half or more.